Pasteurization of food, especially of bovine milk is well known. It is used for killing or inactivating microorganisms present in the food to prevent spoilage of the food, by the growth of the microorganisms in the food. Pasteurization occurs by heating the food to a specific temperature for a specific period of time so as to reduce the number of viable microorganisms in the food. This process is referred to as thermal pasteurization. Two common methods are known. They involve exposure of milk to a high temperature for a short period of time, followed by immediate cooling. The first method of thermal pasteurization is referred to as High Temperature Short Time (HTST) where milk is exposed to a temperature of approximately 72° C. for 15-20 seconds. The second thermal pasteurization method is referred to as low temperature long time (LTLT) or “Holder-” pasteurization, where milk is heated to 62.5° C. and kept for 30 minutes. These are the only universally approved techniques.
Pasteurization of human milk becomes more and more important. It is currently employed for milk banking where milk is donated, screened and supplied to an infant when milk from the infant's mother is not available.
Human milk is very seldom sterile. Presently, approximately 15% of milk collected at various milk banks has to be thrown away in some countries because it contains pathogenic bacteria such as S. aureus, Enterobacteriacea and Enterococci. Approximately 6% has to be thrown away because the total count of bacteria is over 100,000 colony forming units (CFU/ml). Furthermore, Human immunodeficiency virus (HIV), cytomegalovirus (CMV), Human T-lymphotropic virus (HTLV) and other viruses may be transmitted by human milk and cause infections and diseases. Furthermore, transmission of disease can also be mediated through heat resistant spores that survive thermal pasteurization.
Human milk can be pasteurized by HTST or LTLT methods. Holder Pasteurization is capable of causing a 5-log10 reduction of a variety of bacterial species including Escherichia coli, Staphylococcus epidermidis, Enterobacter cloacae, Bacillus cereus and Staphylococcus aureus in human milk (Czank C, et al, Pediatric Research 2009; 66:374-379). Furthermore, HIV, CMV and HTLV are eliminated by the Holder pasteurization (Orloff S. et al., Journal of Human Lactation 1993; 9:13-17/Hamprecht K. et al., Pediatric Research 2004, 56:529-535/Yamato K. et al, Japanese Journal of Cancer Research 1986; 77:13-15). Therefore, thermal pasteurization minimizes the risk of transmission of diseases via human milk.
However, important, heat labile bioactive components present in human milk can be altered or lost from the milk when it is subjected to thermal pasteurization. Accordingly, there exists a need to provide an improved method of pasteurization of human milk that sufficiently inactivates biological contaminants without altering or inactivating important bioactive components.
Ultraviolet (UV) light treatment has been employed for the pasteurization and decontamination of drinking water, beer, wine and fruit juices, cut and whole fruit and also for air purification and packaging of fresh food. Exposure of substances to UV, or UV treatment, is classified as a non-thermal disinfection method. This has been referred to by some in the art as “UV-” or “Cold Pasteurization”.
Ultraviolet light is defined as electromagnetic radiation having wavelengths shorter than visible light but longer than X-rays. Effective UV treatment of a liquid to be pasteurized requires a sufficient dosage, i.e. sufficient exposure of the biological contaminants to the UV. The degree to which UV penetrates the liquid depends on the solubility, density and turbidity of the liquid.
Previous studies have demonstrated that UV treatment could be used to reduce the microbial load of opaque liquids. However, milk is difficult to treat with UV due to its high absorption coefficient of 300 cm−1 at a wavelength of 254 nm compared to the absorption coefficient of drinking water and beer with 0.1 and 20 cm−1, respectively.
Indeed, various flow-through reactors have been developed to ensure sufficient UV exposure is achieved where large volumes of liquid are to be treated and where the liquids to be treated are turbid and light penetration is limited. Such flow-through reactors are designed to spread the liquid into a thin layer or film, or alternatively, a turbulent flow is imparted to the liquid which is caused to flow around the UV source thereby exposing the biological contaminants to photons at the interface between the opaque liquid and the photon source. Such apparatuses are described in U.S. Pat. Nos. 5,675,153, 5,567,616, 6,540,967, 6,576,201 and WO 01/37675.
However, there exist a number of disadvantages associated with current methods and devices for pasteurization of bovine milk or fruit juice that make their application to pasteurization of human milk unworkable.
Firstly, present methods are directed towards the treatment of large volumes of milk which are required to be pumped from a source to a UV reactor and subsequently recirculated or passed through a plurality of reactors. Human milk can only be collected in small volumes and such small volumes would be lost in those large reactors.
Secondly, other problems associated with the requirement to pump milk through a reactor include: stasis of the milk within certain sections of the apparatus which permits collection and growth of biological contaminants; deposition of milk solids upon the surfaces of the reactor which can lead to impedance of UV penetration and difficulty in cleaning the apparatus; and undesirable properties being imparted to the milk such as the formation of butter from coalescence of milk fat globules resulting from turbulent flow applied to the milk. These devices can be difficult to maintain.
Another problem faced by present methods of pasteurizing human milk is a reduction and/or loss of activity of various important bioactive components present in human milk. Current methods for pasteurization of human milk, such as Holder pasteurization, are aimed at reducing the bacterial load of human milk without consideration of maintaining an effective level of important bioactive components in the milk. Pasteurization of human milk is based on the technology developed by the dairy industry. The aim of the dairy industry is to reduce the enzymatic activity in bovine milk to increase shelf-life. In human milk the enzymatic activity is needed to transfer the whole benefit of human milk to the infant.
Human milk has been shown to inhibit the growth of Escherichia coli, Staphylococcus aureus and Candida spp. This bacteriostatic property of human milk is thought to be predominantly due to immunological proteins including lactoferrin, lysozyme and sIgA. Lactoferrin is an iron-binding protein that reduces the availability of free iron required by iron-dependent pathogens such as E. coli and therefore inhibits their growth, as well as disrupting the bacterial cell membrane by binding to the lipid-A portion of lipopolysaccharides on the bacterial cell surface. Lysozyme lyses the cell walls of most gram-positive bacteria such as S. aureus by catalyzing the hydrolysis of specific bonds between N-acetylglucosamine and N-acetylmuramic acid. While lysozyme alone is bacteriostatic, an in vitro study showed that in presence of lactoferrin it is also bactericidal and can kill some gram-negative bacteria. Secretory IgA (sIgA) is an antibody, which is secreted specifically in response to the pathogens the mother and infant are exposed to and therefore, is boosting the infant's immune defence system. sIgA is more able to persist in the intestinal tract than other immunoglobulins due to its resistance to proteolytic enzymes. Although sIgA has no known antimicrobial activity in human milk it enhances the antimicrobial activity of lactoferrin and lysozyme and it plays a major role in the infant's immune defence when digested. The activity and retention of such bioactive components can be adversely impacted using thermal pasteurization.
The PCT application WO 2014/094189, filed Dec. 13, 2013 and claiming two Australian priority dates, refers to a method of pasteurizing small volumes of a human milk product and an apparatus for the same that can be conveniently used by breast feeding mothers, in milk banks, in hospitals and in other clinical settings and that overcomes the above mentioned problems. The method described in this unpublished application especially preserves or retains important bioactive components while sufficiently inactivates biological contaminants in human milk. This is achieved by exposing a milk product to ultraviolet light (UV) and imparting a vortical flow to the milk product to facilitate exposure of the contaminant in the milk product to the UV light. The apparatus for inactivating or reducing an amount of a biological contaminant in a human milk product comprises a container for containing a volume of a human milk product, a UV light source arranged outside of or inside the container such that the human milk product is exposed to UV light; and a means to apply a vortical flow to said milk product retained inside said container so as to facilitate exposure of the contaminant to the UV light source.
As used herein “vortical flow” refers to a flow of liquid wherein the liquid flows in layers in a rotary or spinning motion about an imaginary axis. The axis may be straight or curved. There may be some disruption or mixing in the flow between layers and some turbulence which may occur at various points in the flow of a liquid within a container but the majority of the liquid flows in a vortical fashion.
The vortical flow may be imparted by placing a magnetic bar into the milk container and by rotating the magnetic bar with an appropriate device. It is suggested to use a magnetic stirrer. A balance is applied in creating a fast enough flow for optimal microorganism exposure to the UV-C photons and minimizing the risk of damaging the human milk. This can be achieved by adjusting the revolution speed and/or the method of stirring. Furthermore the size and shape of the stirring means may be adjusted to reduce shear forces. It is also suggested to use a rotating container.
The method and apparatus preferably inactivate or reduce the amount of a biological contaminant present in human milk, wherein the contaminant is selected from E. coli, Staphylococcus spp., Streptococcus spp., Bacillus spp., Enterococcus spp. and Enterobacter spp. Preferably, they additionally or alternatively inactivate or reduce the amount of a biological contaminant present in human milk, wherein the contaminant is selected from CMV, HIV and HTLV.
As used herein, the term “biological contaminant” refers to but is not limited to micro-organisms such as viruses, bacteria, protozoa, yeasts, spores, moulds and algae. Such biological contaminants can include viruses (including viral nucleic acids) selected from but not limited to B-type (retrovirus-like particles), Coxsackievirus B3, Cytomegalovirus (CMV), Ebola virus, Echovirus 18, Epstein-Barr virus (EBV), Hepatitis B virus, Hepatitis C virus, Hepatitis E virus, Herpes simplex virus type 1, Human herpesvirus 6, Human herpesvirus 7, Human immunodeficiency virus (HIV) type 1 (and 2), Human T-lymphotropic virus (HTLV), Human papillomavirus 16, Rotavirus, Rubella virus, Sin nombre (no name) hantavirus RNA, Transfusion-transmission virus (TTV), Varicella-zoster virus, West Nile virus; Bacteria and fungi including but not limited to Staphylococcus spp., Streptoccoccus spp., Bascillus spp., Campylobacter spp., Enterococcus spp. and Enterobacter spp., E. coli, Bacillus cereus, Borrelia burgdorferi, Brucella melitensis, Burkholderia pseudomallei, Candida albicans, Citrobacter freundii, Coxiella burnetti, Enterbacter aerogenes, E. cloaca, Klebsiella pneumonia, Lactobacillus gasseri, Enterococcus faecium, Leptospira australis, Listeria monocytogenes, Mycobacterium paratuberculosis, Mycobacterium tuberculosis, Pseudomonas Aeruginosa, Salmonella Kottbus, Salmonella panama, Salmonella senfrenberg, Salmonella typhimurium, Serratia marcescens, Staphylococcus aureus, Staphylococcus epidermis and Streptococcus agalactiae; Parasites including but not limited to Necator americanus, Onchocerca volvulus, Schistosoma mansoni, Strongyloides fulleborni, Toxoplasma gondii, Trichinella spiralis, and Trypanosoma cruzi. 
As used herein, the term “inactivate” (and forms thereof) means the actual destruction, eradication of a contaminant, or a direct or indirect effect on the contaminant that substantially inhibits its ability to replicate or otherwise to adversely affect a living recipient.
As used herein the term “reduce” (and variants thereof) when applied to a biological contaminant refers to a lowering in the amount of biological contaminant or a reduction in the number of contaminants that are active and/or capable of replicating and/or infecting an individual.